Numerical simulation of the impact of casing on the buried metal pipeline cathodic protection potential

Abstract Metal casings shield the cathodic protection current and detection signals of buried metal pipelines, making the corrosion protection and detection technology of pipelines at the casing one of the challenges for safe operation and integrity evaluation of pipelines. This paper uses the primary current distribution physics interface in the COMSOL Multiphysic simulation software to study the effects of the coating quality of the casing and pipeline, the installation of sacrificial anodes in the casing, the conductivity of the electrolyte, and defects in the pipeline coating in the casing on the pipeline potential. The influence of distribution. The results show that: The coating quality of the outer surface of the casing and the pipe inside the casing has a great influence on the cathodic protection potential of the pipeline. The better the coating quality, the more negative the cathodic protection potential is, and the less cathodic protection current required by the pipeline, so the power consumption of the forced current law is reduced, and the service life of the sacrificial anode is longer. Installing sacrificial anodes in the casing has a positive effect on the cathodic protection of this special pipe section. The conductivity of the electrolyte in the casing has a certain impact on the cathodic protection potential of the pipeline. When the conductivity of the internal electrolyte is greater, the protective potential of the pipeline becomes more negative. However, impurities such as soil, groundwater, and silt make the pipeline more susceptible to corrosion, so keeping the annular space relatively dry is an important prerequisite for anti-corrosion. When there is a coating defect on the inner and outer pipes of the casing, the potential at the damaged point will have a potential peak. The larger the potential peak difference, the more serious the coating defect is.